In certain operations involving data storage and retrieval, the stored data must be updated periodically even though it is being read continually. Such updating operations generally have inefficiencies resulting from delays in loading updated data while waiting for read operations to be completed and delays in subsequent read operations while updated data is being loaded and verified.
One solution to this problem is to employ redundant memories. In a redundant memory system, one memory contains the current data for read operations while the other memory is loaded with updated data as it is received. When the second memory has been loaded and the updated data has been verified, the second memory is switched over as the new current data memory for read operations. This method of alternating redundant memories works well provided each updated memory contains a complete data map. However, this method is not satisfactory for partial loads of updated data.
Therefore, a need has been identified for an improved method and apparatus for updating data in a memory that is being read continually. In such a system it is desirable that delays in loading the updated data, in verifying the updated data, and in reading from the memory while it is being updated be reduced or eliminated.